Influence of the Isolation Method on the Technofunctional Properties of Protein Isolates from Lupinus angustifolius L

The technofunctional properties of 2 protein isolates from Lupinus angustifolius L. Vitabor isolated by different procedures were investigated. The lupin protein isolate prepared by aqueous alkaline extraction with subsequent isoelectric precipitation (ILP) showed a significantly higher degree of protein denaturation and lower denaturation temperatures than the one obtained by aqueous salt-induced extraction followed by dilutive precipitation (MLP) as determined by differential scanning calorimetry. Rheological investigations revealed higher firmness and a viscoelastic solid-like behavior of ILP, in contrast to MLP that showed viscoelastic, liquid-like properties. Protein solubility of MLP was higher compared to ILP and solubility minima were slightly different for both lupin protein isolates. The protein isolates exhibited different technofunctional properties with ILP showing higher water binding capacity, lower oil binding capacity and lower emulsifying capacity than MLP. This reflects the different putative application of both lupin protein isolates as food ingredients, for example for ILP as a moisture enhancer and for MLP as a “natural” emulsifier in mixed food systems.